The 'autobiography' of Claudius continues (from Claudius's accession after Caligula's death, to his own death in 54) in Claudius the God (1935). The sequel also includes a section written as a biography of Herod Agrippa, contemporary of Claudius and future King of the Jews. The two books were adapted by the BBC into an award-winning television serial, I, Claudius.

Claudius was the fourth Emperor of Rome (r. 41–54 AD). Historically, Claudius' family kept him out of public life until his sudden coronation at the age of forty nine. This was due to his being perceived as being a dolt due to his stammering, limp and other nervous tics. This made others see him as mentally deficient and also therefore not a threat to his ambitious relatives. Even as his symptoms begin to wane in his teenage years, he runs into trouble for his work as a budding historian. His work on a history of the civil wars was too truthful and too critical of the reigning emperor Augustus, and his mother and grandmother quickly put a stop to it. This episode reinforced their initial suspicions that Claudius was not fit for public office. This is how he was defined by scholars for most of history, and Graves uses these peculiarities to develop a sympathetic character whose survival in a murderous dynasty depends upon his family's incorrect assumption that he is a harmless idiot.

Graves's interpretation of the story owes much to the histories of Gaius Cornelius Tacitus, Plutarch, and (especially) Suetonius (Lives of the Twelve Caesars). Graves translated Suetonius before writing the novels. Graves claimed that after he read Suetonius, Claudius came to him in a dream one night and demanded that his real story be told. The life of Claudius provided Graves with a way to write about the first four Emperors of Rome (Augustus, Tiberius, Caligula, and Claudius) from an intimate point of view.

In addition, the real Claudius was a trained historian and is known to have written an autobiography (now lost) in eight books that covered the same time period. I, Claudius is a first-person narrative of Roman history from the reigns of Augustus to Caligula; Claudius the God is written as a later addition documenting Claudius' own reign.

Graves provides a theme for the story by having the fictionalised Claudius describe a visit to Cumae, where he receives a prophecy in verse from the Sibyl, and an additional prophecy contained in a book of "Sibylline Curiosities". The latter concerns the fates of the "hairy ones" (i.e. The Caesars – from the Latin word "caesar", meaning "a fine head of hair") who are to rule Rome. The penultimate verse concerns his own reign, and Claudius assumes that he can tell the identity of the last emperor described. From the outset, then, Graves establishes a fatalistic tone that plays out at the end of Claudius the God, Claudius predicts his own assassination and succession by Nero.

At Cumae, the Sibyl tells Claudius that he will "speak clear." Claudius believes this means that his secret memoirs will be one day found, and that he, having therein written the truth, will speak clearly, while his contemporaries, who had to distort their histories to appease the ruling family, will seem like stammerers. Since he wishes to record his life for posterity, Claudius chooses to write in Greek, since he believes that it will remain "the chief literary language of the world." This enables Graves to offer explanations of Latin wordplay or etymologies that would be unnecessary for native Latin speakers.

Claudius establishes himself as the author of this history of his family, and insists on writing the truth, which includes a heavy critique of the now deified Augustus and especially Livia.

During the prosperous reign of Augustus, he is plagued by personal losses as his favored heirs, Marcellus, Marcus Agrippa, Gaius Caesar and Lucius Caesar, die at varying points. Claudius reveals that these untimely deaths are all the machinations of Augustus' cold wife Livia, who seeks to make her son Tiberius succeed Augustus.

As these intrigues occur, the sickly Tiberius Claudius is born and quickly shunned and mocked by his family. Only his brother Germanicus and his cousin Postumus treat him with any kindness. He eventually is given a great tutor Athenodorus, who fosters a love of history and republican government in Claudius. During this early age Claudius is advised by his idol Asinius Pollio to play the fool to survive.

Later, Postumus is framed for raping Livilla and beating his niece Aemilia and banished to an island, but Postumus relays the truth to Claudius. Claudius relays the truth to Germanicus, who convinces Augustus of Postumus' innocence. Relenting, Augustus removes Postumus for a double named Clemens and secretly writes a will restoring Postumus as his heir. But Livia manages to discover this and poisons Augustus.

Following the death of Augustus, Tiberius is declared Emperor, but the legions of Germany refuse to accept Tiberius and instead declare Germanicus as his Emperor. Germanicus, shocked and confused, refuses, instead he sends his wife and youngest son Caligula away and asks Claudius for an enormous sum of money to pay the soldiers. Claudius agrees and pretends that they are gambling debts. With the money and the return of Caligula, Germanicus ends the mutiny and has several successful campaigns in Germany.

In the midst of this, Claudius is informed that Postumus is alive, and secretly forming a resistance group to take back his rightful place in Rome. But Claudius' letters to Germanicus about Postumus are intercepted by Livia. Postumus is later captured and executed by Tiberius. Livia, recognizing that Claudius is a threat, sends him to Carthage to avoid contact with Germanicus.

Growing to fear Germanicus more and more, Tiberius sends a hostile governor, Gnaeus Calpurnius Piso, to spy on Germanicus. Germanicus soon becomes plagued by witchcraft, before dying of poison. It is later revealed that Germanicus' own son Caligula was the instigator of the witchcraft.

As Tiberius becomes more hated, he increasingly relies on his Praetorian Captain Sejanus who is able to make Tiberius fear Germanicus' wife Agrippina and his own son Castor. Sejanus secretly plots with Livilla to usurp the monarchy by poisoning Castor and beginning to remove any ally of Agrippina and her sons. Agrippina only survives due to the protection of Livia, who holds vital information of Augustus' true opinion of Tiberius.

Livia then has a surprising dinner, to which Claudius and Caligula are invited. She predicts that Caligula will become Emperor (not Caligula's older brothers) and that Claudius will succeed him. Livia begs Claudius to swear to make her a goddess (she believes it will grant her a blissful afterlife), which he agrees to. Claudius later is invited to Livia on her deathbed and reveals that Caligula betrayed his promise. Claudius swears that Livia will become the Queen of Heaven, which moves Livia before dying to declare he is no fool.

Tiberius, now free of Livia, loses all compunction and executes hundreds, including banishing Agrippina and her son Nero, while Agrippina's son Drusus is starved to death in Rome. Sejanus is now given full command of the city and is the de facto ruler of Rome. But Tiberius is alerted to Sejanus' treachery by a letter from Antonia. Tiberius now allies himself with Caligula, whom he calls a poisonous snake, and transfers control to the more wicked Macro. Sejanus is killed along with his children. Claudius survives despite being married to Sejanus' sister, and quickly divorces his wife. Livilla is locked in a room by her mother Antonia and starved to death, Antonia punishes herself for having raised Livilla by listening to her daughter die.

Now old and feeble, Tiberius is smothered to death by Macro, after earlier having appeared to have died. Caligula is declared Emperor and at first appears to be enlightened and kind. To his surprise, Claudius is recalled to Rome from his peaceful life writing history in Capua, living with his prostitute companion Calpurnia. Claudius quickly becomes the butt of many taunts and practical jokes by the Imperial Court. Caligula soon loses his mind, after recovering from a severe illness, and declares himself a god. His behavior becomes more and more irrational as he bankrupts the country and kills thousands.

The madness having reached a tempest is finally quelled by Cassius Chaerea (frequently appearing throughout the book) who kills Caligula, along with his wife and daughter. Claudius horrified, hides behind a curtain and is discovered by a disgruntled Praetorian Guard. The Guards needing an Emperor to be employed bemusedly declare Claudius Emperor. Claudius pleads that he does not want to be an Emperor and wants the Republic restored but the Guards ignore him. Claudius sadly accepts for the sake of his wife and unborn child, and on a whim thinks that as Emperor he will finally have people read his books.

The story begins with an apology by Claudius for ending his first history on a dramatic point, and continues with a brief history of his friend Herod Agrippa. Herod Agrippa was a schoolmate of Claudius and was liked by Claudius' mother Antonia. Herod always finds himself in debts and danger in the East and in Rome. He eventually gains the favor of Caligula and is made King of Bashan. Herod is in Rome when the assassination of Caligula happens and quickly is able to convince Claudius to accept being Emperor to avoid Civil War.

Claudius reluctantly executes Cassius Chaerea and several of the assassins and begins tirelessly working for the sake of Rome. He applies himself to the law courts, and demonstrates his intelligence in being able to locate one of Augustus' lost Eagles. Claudius also begins work on building a harbor in Ostia to help preserve the Romans food supply. Claudius is also able to quell two major mutinies against him and has a successful conquest of Britain.

During this time Herod Agrippa conspires to take over the East as he regards himself as the Messiah. When he announces himself as such he breaks the first commandment by declaring himself as a god. Herod quickly dies a painful death, just as his grand-father had died, but he dies imploring Claudius to forgive him and not to trust anyone.

Throughout Claudius reign he is being unwittingly manipulated by his adulterous and wicked wife Messalina who kills many of her enemies as well as being involved in bribery. She eventually conspires to usurp the monarchy with her lover Gaius Silius. Claudius is distraught and crushed by such news and is given an "Olympian Mixture" in order to manage through the ordeal. Claudius arrests Silius and the leaders of the coup. Messalina is executed without Claudius consent, and Claudius has no reaction during his "Olympian" state, and even bemusedly jokes about being worshipped as a god in Britain.

However, upon being relieved of the "Olympian Mixture" Claudius is crushed. Now deploring his actions Claudius decides that the only way the Republic can be restored is by having a true mad monarch rather than the reign of a benevolent one. Comparing himself to the fable of the frogs who desired a King, Claudius privately refers to himself as "Old King Log" and plays a weak and easily manipulated fool. He then incestuously marries his niece Agrippinilla whom he openly despises. In feeble old age Claudius now excessively enjoys gladiatorial games and frequently is intoxicated and makes himself oblivious to Agrippinilla's schemes to gain power and make her son Nero Emperor. Claudius foreseeing that Nero shall be a terrible ruler, he plans on having his noble son Britannicus removed to live with the Northern Britains and later to return as Rome's savior. But Britannicus refuses to do such, and admits that while he loves the Republic, the Republic is dead and wants to challenge Nero the right to rule Rome as an Emperor. Crushed Claudius agrees knowing that he is sending his son to his death. Claudius resignedly accepts that his death is soon with numerous signs suggesting such.

The I, Claudius novels, as they are called collectively, became massively popular when first published in 1934 and gained literary recognition with the award of the 1934 James Tait Black Prize for fiction. They are probably Graves's best known work aside from his myth essay The White Goddess, his English translation of The Golden Ass and his own autobiography Goodbye to All That. Graves later claimed that they were written only from financial need on a strict deadline. Nonetheless, they are today regarded as pioneering masterpieces of historical fiction.

In November and December 2010, as part of the Classic Serial strand, BBC Radio 4 broadcast a series of six-hour-long episodes of a dramatisation of both novels, adapted by Robin Brooks and directed by Jonquil Panting. Performers were Derek Jacobi, Tom Goodman Hill and full cast. It won the 2012 Audie Award in the "Audio Dramatization" category.[4][5]